The trees are a modern intrusion, but the earthwork beneath them is not. What they surround is a ringfort, a type of enclosed farmstead built in early medieval Ireland, typically between the fifth and twelfth centuries, and used as a defended homestead for a family of some local standing.

The enclosure at Killameen is roughly circular, measuring about 44 metres across at its widest point. It is defined by a round-topped earthen bank, still standing some 2.3 metres high on its outer face, and a V-shaped fosse, the term for a rock-cut or earthen ditch dug around a fortification, running just outside it. The fosse has been partially deepened over time for drainage, which is a practical alteration common on working farmland but one that does complicate any reading of the original profile. Two entrances break the circuit: one on the east side, about 4.4 metres wide and lacking a causeway, which may be original; and one on the west, narrower at 2.1 metres and fitted with a causeway, which is considered modern. The site sits on an east-facing slope, a typical placement for ringforts, which were often sited to catch morning light and to command a view of the surrounding landscape. A minor road curves around the south and west of the enclosure, adding a further layer of boundary to what is already a well-defined piece of ground.